Particulate detergent compositions with improved environmental profiles could, in theory, be designed by eliminating all components from the composition that provide limited, or no, cleaning action. Such compact products would also reduce packaging requirements. However, to achieve this objective is difficult in practice because the manufacture of particulate detergent compositions usually requires the use of components that do not contribute significantly to detergency, but are nevertheless included to structure liquid ingredients into solids, to assist with processing and to improve the handling and stability of the particulate detergent compositions.
In our pending applications, PCT/EP2010/055256 and PCT/EP2010/055257 we propose to solve these problems by manufacturing a new particulate detergent composition. In general, the manufacture is done using a process comprising the steps of drying a surfactant blend, extruding it and cutting the extrudates to form hard core particles with a diameter of greater than 2 mm and a thickness greater than 0.2 mm. These large core particles are then preferably coated, especially with an inorganic coating.
Compositions comprising at least 70 wt % of these coated large particles with extruded surfactant cores differ from prior art extruded detergent compositions in that they have little or no solid structuring material to harden or structure the surfactant core. Instead, they use blends of low moisture surfactants to give hardness. The choice of surfactant allows the particles to give good detergency even without any conventional detergent builder, thus eliminating the need for such builders in the particles. Although the extruded particles are hard enough to cut to the required shape without deformation, they are hygroscopic and would stick together if not coated. It is therefore advantageous to coat the core particles by spraying inorganic material, such as sodium carbonate, onto them, in a fluid bed. The combination of the coating and the large particle size (5 mm diameter) substantially eliminates any tendency to deform or cake and allows production of a novel free-flowing composition of larger than usual detergent particles with excellent smooth and uniform appearance. Surprisingly, despite their large volume and high density, the particles are fast dissolving with low residues and form clear wash liquors with excellent primary detergency.
For fabric washing it is conventional to use a fabric substantive optical whitening agent or fluorescer in the detergent composition. Problems were encountered when a sulphonated fluorescer was added to the core of the particles as described in the above referenced co-pending applications.
GB2076011 notes that some sulphonated optical brighteners are coloured but can be rendered white in the presence of hydroxyl containing compounds. PEG is a suitable hydroxyl containing compound and in admixture with PEG the fluorescers turned from yellow-green to white. The molten mix could be flaked or alternatively it is suggested, but not exemplified, to use it to spray it onto detergent granules in a fluid bed (page 4 line 40).
U.S. Pat. No. 6,159,920 makes a fluorescer coated detergent particle by spaying on a mixture of fluorescer and nonionic surfactant. It is essential that the coating is anhydrous. Spraying is done in a Lödige mixer. A preferred fluorescer is Tinopal CBS.
DE 10 2006 034 900 A1 discloses a method of applying fluorescer to a porous detergent powder.